American Sign Language (ASL)-manual (hand) language with its own syntax and grammar used primarily by people who are deaf.

anosmia-absence of the sense of smell.

aphasia-total or partial loss of ability to use or understand language; usually caused by stroke, brain disease, or injury.

aphonia-complete loss of voice.

apraxia-inability to make a voluntary movement in spite of being able to demonstrate normal muscle function.

articulation disorder-inability to correctly produce speech sounds (phonemes) because of imprecise placement, timing, pressure, speed, or flow of movement of the lips, tongue, or throat.

assistive devices-technical tools and devices such as alphabet boards, text telephones, or text-to-speech conversion software used to assist people with physical or emotional disorders in performing certain actions, tasks, and activities.

audiologist-a healthcare professional trained to identify and measure hearing impairments and related disorders using a variety of tests and procedures.

auditory brainstem response (ABR) test-test used for hearing in infants and young children, or to test for brain functioning in unresponsive patients.

auditory nerve-eighth cranial nerve that connects the inner ear to the brainstem.

auditory perception-ability to identify, interpret, and attach meaning to sound.

auditory prosthesis-device that substitutes or enhances the ability to hear.

augmentative devices-tools that help individuals with limited or absent speech to communicate.

aural rehabilitation-techniques used with people who are hearing impaired to improve ability to speak and to communicate.

autism-brain disorder that begins in early childhood and persists throughout adulthood; affects three crucial areas of development: communication, social interaction, and creative or imaginative play.

autoimmune deafness-hearing loss in an individual that may be associated with a tissue-causing disease, such as rheumatoid arthritis or lupus.

balance-biological system that enables individuals to know where their bodies are in the environment and to maintain a desired position; normal balance depends on information from the labyrinth in the inner ear, and from other senses such as sight and touch, as well as from muscle movement.

balance disorder-disruption in the labyrinth, the inner ear organ that controls the balance system allowing individuals to know where their bodies are in the environment.

barotrauma-injury to the middle ear caused by a reduction of air pressure.

benign paroxysmal positional vertigo (BPPV)-balance disorder that results in a sudden onset of dizziness, spinning, or vertigo that occurs when suddenly moving the head from one position to another.

brainstem implant-auditory prosthesis that bypasses the cochlea and auditory nerve to help individuals who cannot benefit from a cochlear implant because the auditory nerves are not working.

cochlea-snail-shaped structure in the inner ear that contains the organ of hearing.

cochlear implant-medical device that bypasses damaged structures in the inner ear and directly stimulates auditory nerve to allow some deaf individuals to learn to hear and interpret sounds and speech.

computed tomography scan (Also called a CT or CAT scan.)-a diagnostic imaging procedure that uses a combination of x-rays and computer technology to produce cross-sectional images (often called slices), both horizontally and vertically, of the body. A CT scan shows detailed images of any part of the body, including the bones, muscles, fat, and organs. CT scans are more detailed than general x-rays.

conductive hearing impairment-hearing loss caused by dysfunction of the outer or middle ear.

cued speech-method of communication that combines speech reading with a system of handshapes placed near the mouth to help deaf or hard-of-hearing individuals differentiate words that look similar on the lips.

cytomegalovirus (congenital)-one group of herpes viruses that infect humans and can cause a variety of clinical symptoms including deafness or hearing impairment; infection with the virus may be either before or after birth.

parosmia-any disease or perversion of the sense of smell, especially the subjective perception of odors that do not exist.

perception (hearing)-process of knowing or being aware of information through the ear.

perilymph fistula-leakage of inner ear fluid to the middle ear that occurs without apparent cause or is associated with head trauma, physical exertion, or barotrauma.

phonology-study of speech sounds.

positron emission tomography (PET) scan-a computer-based imaging technique that uses radioactive substances to examine body processes. For example, a PET scan of the heart provides information about the flow of blood through the coronary arteries to the heart.

postlingually deafened-individual who becomes deaf after having learned language.

prelingually deafened-individual who is either born deaf or who lost hearing early in childhood, before learning language.

presbycusis-loss of hearing that gradually occurs because of changes in the inner or middle ear in individuals as they grow older.

smell disorder-inability to perceive odors that may be temporary or permanent.

sound vocalization-ability to produce voice.

spasmodic dysphonia-momentary disruption of voice caused by involuntary movements of one or more muscles of the larynx or voice box.

specific language impairment (or SLI)-difficulty with the organized-symbol-system communication in the absence of problems such as mental retardation, hearing loss, or emotional disorders.

speech-making definite vocal sounds that form words to express thoughts and ideas.

speech disorder-defect or abnormality that prevents an individual from communicating by means of spoken words.

speech processor-part of a cochlear implant that converts speech sounds into electrical impulses to stimulate the auditory nerve.

speech-language pathologist-health professional trained to evaluate and treat people who have voice, speech, language, or swallowing disorders, including hearing impairment, that affect their ability to communicate.

stuttering-frequent repetition of words or parts of words that disrupts the smooth flow of speech.

sudden deafness-loss of hearing that occurs quickly from such causes as explosion, a viral infection, or the use of some drugs.

swallowing disorders-any of a group of problems that interfere with the transfer of food from the mouth to the stomach.

syndromic hearing impairment-hearing loss or deafness that is inherited or passed through generations of a family.

vertigo-illusion of movement; sensation that the external world is revolving around an individual (objective vertigo) or that the individual is revolving in space (subjective vertigo).

vestibular neuronitis-infection at the vestibular nerve.

vestibular system-system in the body that is responsible for maintaining the body's orientation in space, balance, and posture; also regulates locomotion and other movements and keeps objects in visual focus as the body moves.

vestibule-bony cavity of the inner ear.

vibrotactile aids-mechanical instruments that help individuals who are deaf detect and interpret sound through the sense of touch.

vocal cords (vocal folds)-muscularized folds of mucous membrane that extend from the larynx (voice box) wall; enclosed in elastic vocal ligament and muscle that control the tension and rate of vibration of the cords as air passes through them.

vocal cord paralysis-inability of one or both vocal folds (vocal cords) to move because of damage to the brain or nerves.

vocal tremor-trembling or shaking of one or more of the muscles of the larynx resulting in an unsteady-sounding voice.

voice-sound produced by air passing out through the larynx and upper respiratory tract.

voice disorders-group of problems involving abnormal pitch, loudness, or quality of the sound produced by the larynx (voice box).

Waardenburg syndrome-hereditary deafness that is characterized by hearing impairment, a white shock of hair, and/or distinctive blue color to one or both eyes, as well as wide-set inner corners of the eyes; balance problems are also associated with some types of Waardenburg syndrome.